: Multiple versions of the LabVIEW Run-Time Engine can coexist on one machine as long as the major version numbers differ (e.g., you can have 8.5.1 and 2021 installed simultaneously).
: NI no longer actively hosts very old runtimes on their main site, but they keep them in their legacy download archives . You may need a free NI account. labview runtime engine 85 1 download 2021